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Add lerp method

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ltdk 2021-06-01 22:50:42 -04:00
parent 625d5a693e
commit f310d0e500
2 changed files with 56 additions and 0 deletions
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28
library/std/src/f32.rs
View file

@ -876,4 +876,32 @@ impl f32 {
pub fn atanh(self) -> f32 {
0.5 * ((2.0 * self) / (1.0 - self)).ln_1p()
}
/// Linear interpolation between `start` and `end`.
///
/// This enables the calculation of a "smooth" transition between `start` and `end`,
/// where start is represented by `self == 0.0` and `end` is represented by `self == 1.0`.
///
/// Values below 0.0 or above 1.0 are allowed, and in general this function closely
/// resembles the value of `start + self * (end - start)`, plus additional guarantees.
///
/// Those guarantees are, assuming that all values are [`finite`]:
///
/// * The value at 0.0 is always `start` and the value at 1.0 is always `end` (exactness)
/// * If `start == end`, the value at any point will always be `start == end` (consistency)
/// * The values will always move in the direction from `start` to `end` (monotonicity)
///
/// [`finite`]: #method.is_finite
#[must_use = "method returns a new number and does not mutate the original value"]
#[unstable(feature = "float_interpolation", issue = "71015")]
pub fn lerp(self, start: f32, end: f32) -> f32 {
// consistent
if start == end {
start
// exact/monotonic
} else {
self.mul_add(end, (-self).mul_add(start, start))
}
}
}

28
library/std/src/f64.rs
View file

@ -879,6 +879,34 @@ impl f64 {
0.5 * ((2.0 * self) / (1.0 - self)).ln_1p()
}
/// Linear interpolation between `start` and `end`.
///
/// This enables the calculation of a "smooth" transition between `start` and `end`,
/// where start is represented by `self == 0.0` and `end` is represented by `self == 1.0`.
///
/// Values below 0.0 or above 1.0 are allowed, and in general this function closely
/// resembles the value of `start + self * (end - start)`, plus additional guarantees.
///
/// Those guarantees are, assuming that all values are [`finite`]:
///
/// * The value at 0.0 is always `start` and the value at 1.0 is always `end` (exactness)
/// * If `start == end`, the value at any point will always be `start == end` (consistency)
/// * The values will always move in the direction from `start` to `end` (monotonicity)
///
/// [`finite`]: #method.is_finite
#[must_use = "method returns a new number and does not mutate the original value"]
#[unstable(feature = "float_interpolation", issue = "71015")]
pub fn lerp(self, start: f64, end: f64) -> f64 {
// consistent
if start == end {
start
// exact/monotonic
} else {
self.mul_add(end, (-self).mul_add(start, start))
}
}
// Solaris/Illumos requires a wrapper around log, log2, and log10 functions
// because of their non-standard behavior (e.g., log(-n) returns -Inf instead
// of expected NaN).